1. Art Field of the Invention
The invention is directed to an improved fuel injection apparatus for an internal combustion engine,
2. Description of the Prior Art
A fuel injection apparatus of this kind is known from EP 0 987 431 A2. has a high-pressure fuel pump and a fuel injection valve connected to it for each cylinder of the internal combustion engine. The high-pressure fuel pump has a pump piston that delimits a pump working chamber and is driven into a stroke motion by the engine. The fuel injection valve has a pressure chamber connected to the pump working chamber and an injection valve element that controls at least one injection opening; the pressure prevailing in the pressure chamber can move the injection valve element in the opening direction counter to a closing force in order to open the at least one injection opening. A first electrically actuated control valve is provided, which controls a connection of the pump working chamber to a relief chamber. A second electrically actuated control valve is also provided, which controls a connection of a control pressure chamber to a relief chamber. The control pressure chamber is connected to the pump working chamber via a throttle restriction. The control pressure chamber is defined by a control piston, which is supported on the injection valve element and is acted on in a closing direction of the injection valve element by the pressure prevailing in the control pressure chamber. For an injection of fuel, the first control valve is closed and the second control valve is opened so that high pressure cannot build up in the control pressure chamber and the fuel injection valve can open. When the second control valve is open, though, fuel flows out of the pump working chamber via the control pressure chamber, thus reducing the fuel quantity available for injection out of the fuel quantity supplied by the pump piston and also reducing the pressure available for the injection. It follows from this that the efficiency of the fuel injection apparatus is not optimal.